Under Armour isn't cool with teens anymore - and it's becoming a huge problem for the brand

(Under Armour is falling out of favor with teens.AP Photo/Gregory Payan) Under Armour's brand perception among America's youngest consumers is falling.

According to Piper Jaffray's newest Taking Stock of Teens survey, teens just aren't into Under Armour anymore. It was the No. 1 brand that upper-income male teens said they are no longer wearing for the full year, according to the survey.

In a ranking of preferred apparel brands among upper-income male teens, Under Armour fell into 11th place, down from 8th place a year ago. It fell from 6th place into 9th place among average-income male teens.

Under Armour has been losing cachet for a while now.

In a survey of young male consumers by Wells Fargo earlier this year, Under Armour shoes ranked near the bottom in terms of favorability. In a note to investors, the bank's analysts said that only 27% of survey participants ranked Under Armour favorably, while the Curry brand was even lower, at 19%.

For comparison, the young male consumers who were surveyed ranked Adidas at 70%, and Nike at the top with 81%. Participants could check as many boxes as they wanted.

That's not the end of the bad news for Under Armour, however. In another survey question, the bank asked which brands the participants were more interested in purchasing than before, and which they were less interested in purchasing.

About 33% of the respondents said they were less likely to buy Under Armour shoes, and only 17% said they were more likely to buy them. That put Under Armour dead last with a net rating of -17%.

Under Armour shoe sales have basically flatlined this year. The basketball star Kevin Durant, signed with rival Nike,said in an interview in August that "everybody knows" that "nobody wants to play in Under Armours."

Shoes are a core business for athletic brands - they account for 65% of Nike's sales but are just 20% of Under Armour's business.